“Unequivocal.”That’s quite a claim in this skeptical era, so it’s been enlightening to watch the unraveling of the absolute certainty of global warming caused by man. Now even authors of the 2007 United Nations report that “warming of the climate system is unequivocal” have backed off its key assumptions and dire warnings.

Science is having its Walter Cronkite moment. Back when news in America was delivered by just three television networks, Walter Cronkite could end his evening broadcast by declaring, “And that’s the way it is.” The Intergovernmental Panel on Climate Change (IPCC) report likewise purported to proclaim the final word, in 3,000 pages that now turn out to be less scientific truth than political cover for sweeping economic regulations.

Equivocation has replaced “unequivocal” even among some of the scientists whose “Climategate” emails discussed how to suppress dissenting views via peer review and avoid complying with freedom-of-information requests for data.

Phil Jones, the University of East Anglia scientist at the center of the emails, last week acknowledged to the BBC that there hasn’t been statistically significant warming since 1995. He said there was more warming in the medieval period, before today’s allegedly man-made effects. He also said “the vast majority of climate scientists” do not believe the debate over climate change is settled. Mr. Jones continues to believe in global warming but acknowledges there’s no consensus.Some journalistic digging into the 2007 U.N. climate change report revealed that its most quoted predictions were based on dubious sources. The IPCC now admits that its prediction that the Himalayan glaciers might disappear by 2035 was a mistake, based on an inaccurate citation to the World Wildlife Foundation. This advocacy group was also the basis for a claim the IPCC has backed away from—that up to 40% of the Amazon is endangered. The IPCC report mistakenly doubled the percentage of the Netherlands currently below sea level. John Christy, a former lead author of the IPCC report, now says the “temperature records cannot be relied on as indicators of global change.” As the case collapsed, the top U.N. climate-change bureaucrat, Yvo de Boer, announced his resignation last week.

The climate topic is important in itself, but it is also a leading indicator of how our expectation of full access to information makes us deeply skeptical when we’re instead given faulty or partial information. In just three years since the report was issued, we have gone from purported unanimity among scientists to a breakdown in any consensus. Opinion polls reflect this U-turn, with growing public skepticism.

Skeptics don’t doubt science—they doubt unscientific claims cloaked in the authority of science. The scientific method is a foundation of our information age, with its approach of a clearly stated hypothesis tested through a transparent process with open data, subject to review. The IPCC report was instead crafted by scientists hand-picked by governments when leading politicians were committed to global warming. Unsurprisingly, the report claimed enough certainty to justify massive new spending and regulations.

Some in the scientific community are now trying to restore integrity to climate science. “The truth, and this is frustrating for policy makers, is that scientists’ ignorance of the climate system is enormous,” Mr. Christy wrote in the current issue of Nature. “There is still much messy, contentious, snail-paced and now, hopefully, transparent, work to do.” Mr. Christy also makes the good point that groupthink—technically known as “informational cascades”—is a particular risk for scientists. He proposes a Wikipedia-like approach in which scientists could openly contribute and debate theories and data in real time.

The unraveling of the case for global warming has left laymen uncertain about what to believe and whom to trust. Experts usually know more than amateurs, but increasingly they get the benefit of the doubt only if they operate openly, without political or other biases.

We need scientists who apply scientific objectivity, or the closest approximation of it, and then present their information with enough transparency that people can weigh the evidence. Instead of a group of scientists anointed by the U.N. telling us what to think, the spirit of the age is that scientists need to provide open access to information on which others can make policy decisions.

The lesson of the chill of the global-warming consensus is this: Those who want to persuade others of the truth as they see it need to make their case as transparently as possible. Technology enables access to information and leads us to expect open debates, conducted honestly and in full view. This is inconvenient for those who want to claim unequivocal truth without having the evidence. But that’s the way it is.With thanks to WSJ